The present invention relates to a microscopic defect inspection apparatus and a method thereof, as well as a positional shift or gap calculation circuit therefor, for detecting or inspecting very fine defects, such as very fine or minute foreign substances or matters and/or pattern defects on a subject, for example on substrates, in particular, the substrate which has repetitive patterns thereon, such as a semiconductor wafer, a reticule with phase sifter and a TFT substrate.
Conventional arts relating to a method for inspecting defects on repetitive patterns were already known, for example, in Japanese Patent Laying-Open No. Hei 5-264467 (1993) (Conventional art 1), Japanese Patent Laying-open No. Hei 5-6928 (1993) (Conventional art 2) and Japanese Patent Laying-Open No. Hei 10-74812 (1998) (Conventional art 3).
In those conventional arts 1, 2 and 3, there are described inspection of defects on the repetitive patterns, by detecting the positional shift or gap between video picture inputted and picture delayed by a pitch of the repetitive pattern so as to compensate or correct it. In particular, according to the conventional art 2, in the pattern inspection of detecting two (2) pictures formed to be the same pattern, so as to be compared with after being adjusted in positions thereof, thereby to determine the defects at the portions being inconsistent with each other on those video pictures, there is described that an amount of positional shifts or gaps on the pictures is detected at every predetermined time period, and that compensation or correction of those positional gaps is made dependent upon the amount of positional gaps up to the previous one.
Also, in the conventional art 3, there are described an inspection method for patterns as an object or target for inspection, wherein a video signal is detected from the repetitive patterns to be inspected, so as to produce a statistic video signal of the repetitive pattern therefrom, and then the defects or potential or pseudo-defects lying on the subject pattern are extracted by comparing this statistic video signal produced as a reference to the above-mentioned video signal detected after adjusting the positions thereof; and also an inspection method for the subject, i.e., the patterns to be inspected, wherein the video signal is detected from the repetitive patterns to be inspected, so as to produce a statistic information indicated by a statistic amount of the repetitive pattern from the detection video signal, and then the defects or potential or pseudo-defects lying on the subject pattern are extracted by treating a decision process upon the difference on video, being obtained by adjusting in position and then comparing the video signals of the above-mentioned repetitive patterns with each other, upon the basis of criteria being obtainable from the produced statistic information mentioned above. Further, in the conventional art 3, there is also described that the patterns as the subject are inspected with using an electron pictures thereof.
Further, a conventional art relating to a video picture detection system with using ultraviolet rays is already known in Japanese Patent Laying-Open No. Hei 10-177139 (1998) (Conventional art 4). In this conventional art 4, it comprises correcting mechanisms for primary and higher dimensions on various kinds of aberrations, including aberrations in the longitudinal and horizontal directions of spectrum, spreading over a wide band region from the ultraviolet to far-ultraviolet in the effective wavelength thereof, and there is further described a wide band ultraviolet ray video system, apply both principles of reflection and refraction therein, having a focus lens group composed of a plurality of lenses for providing the high dimensional correction on the video distortion within the same spectrum band or the aberration which causes change of color due to the chromatic aberration, a field lens group having at least two (2) refraction characteristics being different to each other, and further a catadioptric group.
For detecting the defects, such as breaks or short-circuits of lines on the wiring patterns, the picture video must be detected on the patterns as the target for inspection. However, the wiring patterns on semiconductor devices or the like are in a tendency of minimization, and the resolution is short or high on the picture which is obtained through an optical microscope under a visual light rays, therefore it is impossible to analyze the fine or microscopic patterns, then there occurs a necessity of using an optical microscope with using far-ultraviolet ray and/or an electron microscope.
However, in the conventional art 4 mentioned in the above, no consideration was taken on an aspect of enabling detection of the defects and/or foreign substances or matters of the very fine or minute patterns, occurring on the substrate as the target of inspection, on which the patterns are formed.
Also, none of the conventional arts 1, 2 and 3 mentioned above makes consideration on an aspect of enabling to detect the video signal having a high resolution through the optical microscope with using the far-ultraviolet ray.
Further, in a case of using the optical microscope with using far-ultraviolet ray and/or the electron microscope, since there occurs a necessity of detecting the video signal while reducing the size of the pixels, the number of the pixels lying within an area or region to be searched for detection and correction of the position shifts or gaps is enlarged or extended in that instance, the scale of circuitry to execute the video processing for detection and corrections of the position gaps is increased up, and the time necessary for that video processing of detection of the position shift and so on, as well.
However, none of the conventional arts 1, 2 and 3 mentioned above pays consideration on an aspect of small-sizing the circuit scale for performing the video processing of detection and correction of the position shift, nor of shortening the video processing time necessary for detection of the position shift and so on, in particular in the case of using the optical microscope with far-ultraviolet ray and/or the electron microscope.
An object according to the present invention, for dissolving the problems mentioned above, is to provide a fine defect inspection apparatus and a method thereof, wherein video processing for detection and correction of the position shift can be conducted upon the video signal detected by using the optical microscope with far-ultraviolet ray and/or the electron microscope, in the enlarged search area or region in which the number of the pixels thereof is increased up, thereby being able to perform the inspection with high reliability, but without failing to detect the very fine true defects erroneously.
Also, other object according to the present invention is to provide a fine defect inspection apparatus and a method thereof, wherein the video processing for detection and correction of the position shift can be conducted upon the video signal detected by using the optical microscope with far-ultraviolet ray and/or the electron microscope, at a high speed with high throughput, but without increasing up the circuit scale, thereby being able to perform the inspection with high reliability, but without failing to detect the very fine true defects erroneously.
Also, further other object according to the present invention is to provide a fine defect inspection apparatus and a method thereof, wherein the video signal detected with a high resolving power can be obtained from the optical microscope with far-ultraviolet ray, at high speed and with high resolution, thereby being able to perform the inspection with high reliability and also with high speed, but without failing to detect the very fine true defects erroneously.
Moreover, further other object according to the present invention is to provide a position shift calculation circuit for realizing the detection of the position gaps within the enlarged search area or region in which the pixel number is increased up, with using a circuit for use in detection of the position shift.
For accomplishing the object(s) mentioned above, in accordance with the present invention, there is provided an apparatus for inspecting fine defects upon a surface of a sample, comprising: a video signal detection portion for outputting video signal corresponding to 0.2 xcexcm or less than that, in pitch size upon picking up of an image of the sample; an A/D converter portion for outputting detection video data through A/D conversion of the video signal outputted from said video signal detection portion; a reference video production circuit portion for producing reference video data to be compared with the detection video data outputted from said A/D conversion portion; a position gap detection circuit portion for detecting position gaps between the detection video data outputted from said A/D converter portion and the reference video data outputted from said reference video production circuit portion, to perform correction thereof; and a comparison circuit portion for comparing the detection video data, being corrected in position gaps thereof within said position gap detection portion, with the reference video data, so as to obtain pseudo-defect point, thereby to output information relating to said pseudo-defect point, wherein said position gap detection circuit portion and said comparison circuit portion are constructed with a circuit element of large scaled integration (LSI).
Also, in accordance with the present invention, there is provided an apparatus for inspecting fine defects upon a surface of a sample, comprising: a video signal detection portion for outputting video signal in parallel through multi-channels upon picking up of an image of the sample; an A/D converter portion for outputting detection video data in parallel through A/D conversion of each of the multi-channel video signal outputted from said video signal detection portion in parallel; a reference video production circuit portion for producing reference video data for the multi-channels in parallel, to be compared with the multi-channel detection video data outputted from said A/D conversion portion in parallel; a position gap detection circuit portion for detecting position gaps between the multi-channel. detection video data outputted in parallel from said A/D converter portion and the multi-channel reference video data outputted in parallel from said reference video production circuit portion, to perform correction thereof; and a comparison circuit portion for executing comparison of the multi-channel detection video data, being corrected in position gaps thereof within said position gap detection portion, with the multi-channel reference video data, so as to obtain pseudo-defect point therefrom, and extraction of information relating to said pseudo-defect point, by parallel processing thereof over the multi-channels.
Further, in accordance with the present invention, there is provided a method for inspecting fine defects upon a surface of a sample, comprising the following the steps: outputting video signal corresponding to 0.2 xcexcm or less than that, in pitch size upon picking up of an image of the sample; outputting detection video data through A/D conversion of said video signal outputted; producing reference video data to be compared with the detection video data outputted; detecting position gaps between the detection video data outputted from said A/D converter portion and the reference video data outputted, to perform correction thereof; and comparing the detection video data, being corrected in position gaps thereof with the reference video data, so as to obtain pseudo-defect point, thereby outputting information relating to said pseudo-defect point, wherein the correction by detecting the position gaps and the outputting the information relating to said pseudo-defect point by obtaining the pseudo-defect point are performed within a circuit element of large scaled integration (LSI).
Furthermore, in accordance with the present invention, there is provided a method for inspecting fine defects upon a surface of a sample, comprising the following steps of: outputting video signal in parallel through multi-channels upon picking up of an image of the sample; outputting detection video data in parallel through A/D conversion of each of said multi-channel video signal outputted in parallel; producing reference video data for the multi-channels to be compared with the multi-channel detection video data outputted in parallel, thereby outputting it in parallel; detecting position gaps between the multi-channel. detection video data outputted in parallel and the multi-channel reference video data outputted in parallel, thereby to perform correction thereof; and executing comparison of the multi-channel detection video data, being corrected in position gaps thereof within said position gap detection portion, with the multi-channel reference video data, so as to obtain pseudo-defect point therefrom, and extraction of information relating to said pseudo-defect point, by parallel processing thereof over the multi-channels.
As was explained in the above, according to the construction mentioned above, the video signal having pixel size equal or less than 0.2 xcexcm is detected by the video signal detection portion from the substrate as the target of inspection, therefore it is possible to perform the inspection with high reliability, but without erroneously failing to detect very fine or minute true defects, such as very fine foreign substances and/or pattern defects, etc., on the very fine patterns (being from 0.3 xcexcm to 0.2 xcexcm or less than that).
Also, with the construction mentioned in the above, wherein the video signal detection portion is constructed so as to comprise an optical irradiation system for irradiating DUV light having wavelength equal or less than 400 nm upon the substrate as a target to be inspected, and an optical detection portion for receiving the reflection light from said substrate to convert it into the video signal, and an image sensor for receiving the light is formed from the TDI image sensor being able to receive the DUV light, therefore the video signal having high resolution can be detected upon the basis of the scattering light or the diffraction light from the very fine defects, being equal or less than 0.1 xcexcm, as a result of this it is possible to perform the inspection with high reliability, but without erroneously failing to detect very fine or minute true defects, such as very fine foreign substances and/or pattern defects, etc.
Further, with the construction mentioned in the above, wherein the video processing, such as the position gap detection and the position gap correction, etc., are processed in parallel within the video processing portion, and further with obtaining high speed being equal or higher than 20 MHz for the video processing within the circuit (LSI) for performing the video processing, the position gap detection and the position gap correction, etc., over the search region which is expanded in the number of pixels when the pixel size is equal or less than 0.2 xcexcm, can be executed at high speed without increasing in the scale of circuitry, and as a result of this it is possible to realize the inspection with high reliability, but without erroneously failing to detect the very fine or minute true defects and at high throughput, by means of the construction of apparatus being simplified therein.
Those and other objects, feature and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings.